Astrophysical Black Holes: A Rapidly Moving Field

Session

Gravitational Waves

26 Jun 2023, 09:30

3. Why are LIGO/Virgo black holes so massive?

Prof. Xian Chen (Peking University)

26/06/2023, 09:30

Talk

Measuring the mass and distance of a gravitational wave (GW) source is a fundamental problem in GW astronomy. The issue is becoming even more pressing since LIGO and Virgo have detected massive black holes that in the past were thought to be rare, if not entirely impossible. The waveform templates used in the detection are developed under the assumption that the sources are residing in a...

39. Accretion flows in AGN dominated by feedback from embedded black holes

Mr Shmuel Gilbaum (Hebrew University of Jerusalem)

26/06/2023, 09:48

Talk

We present new two-fluid models of accretion disks in active galactic nuclei (AGN) that aim to resolve the long-standing problem of Toomre instability in AGN outskirts. In the spirit of earlier work by Sirko Goodman 2003 and others, we argue that Toomre instability is eventually resolved via feedback produced by fragmentation and its aftermath. Unlike past semi-analytic models, which (i) adopt...

4. The susceptible GW sources in the AGN accretion disk

Mr Peng Peng (Peking University)

26/06/2023, 10:06

Talk

Extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals (IMRIs) are important gravitational-wave (GW) sources for the Laser Interferometer Space Antenna (LISA). So far, their formation and evolution are considered to be independent, but recent theories suggest that stellar-mass black holes (sBHs) and intermediate-mass black hole (IMBHs) can coexist in the accretion disk of...

45. Constraining the acceleration of moving binary black holes using gravitational wave

Mr Xinmiao Zhao (Peking University)

26/06/2023, 11:00

Talk

Binary black holes (BBHs) are one of the most important types of gravitational wave (GW) sources. Recent studies show that BBHs may form and merge in the vicinity of a supermassive black hole (SMBH), which results in overestimated masses of black holes due to gravitational and Doppler redshift. One of the distinctive features of these GW sources is that they are accelerating around the SMBH,...

20. SgrA* spin and mass estimates through the detection of an extremely large mass-ratio inspiral

Dr Alejandro Torres Orjuela (TianQin Center (Sun Yat-Sen University))

26/06/2023, 11:18

Talk

Estimating the spin of SgrA$^*$ is one of the current challenges we face in understanding the center of our Galaxy. In the present work, we show that detecting the gravitational waves (GWs) emitted by a brown dwarf inspiraling around SgrA$^*$ will allow us to measure the mass and the spin of SgrA$^*$ with unprecedented accuracy. Such systems are known as extremely large mass-ratio inspirals...

21. Possibility of black hole spin estimation with time-variable “crescent-shaped” shadow in M87

Mr Mikiya Takahashi (University of Tsukuba)

26/06/2023, 11:36

Talk

It is a great challenge to constrain the spin magnitude of the black holes (BHs). We have calculate a radio image of M87 in a flaring state using a part of time-dependent general relativistic radiative transfer code: CARTOON (Takahashi et al. 2022), and found that a time variable "crescent-shaped" shadow appears and its width depends on the BH spin magnitude. Following our previous work...

12. Revisiting Stellar Orbits and the Sgr A* Quadrupole Moment

Yael Alush (The Hebrew University of Jerusalem)

Talk

The "no-hair" theorem can, in principle, be tested at the center of the Milky Way by measuring the spin and the quadrupole moment of Sgr A* with the orbital precession of S-stars, measured over their full periods. Contrary to the original method, we show why it is possible to test the no-hair theorem using observations from only a single star, by measuring precession angles over a half-orbit....